Oxidation of lower aliphatic alcohols



Patented 'Aug. 19, 1947 UNITED STATES PATENT OFFICE OXIDATION OF LOWERALIPHATIC ALCOHOLS David 0. Hull, Kingsport, Tenn., assignor to EastmanKodak Com corporation of New J pany, Rochester, N. Y., a erseyApplication July 8, 1944, Serial No. 544,003

. 6 Claims. 1 This invention relates to thedirect oxidation of organiccompounds, particularly the oxidation of hydroxy compounds such as loweraliphatic alcohols oxidized directly to acids. 7

As pointed out in my U. S. Patent No. 2,287,803 prior art oxidationprocesses have required the employment of relativelyhightemperaturessuch as 300 C. or 100 C. and the application of severalsteps. In other words, the oxidation either has not been direct, or ifthere has been direct conversion, the yields have been very. low. Forexample, considering prior art procedure for con verting ethanol toacetic acid, before my invention it was considered necessary to firstdehydrogenate all of the ethanol and thereafter the aldehydicdehydrogenation product was 'converted to the acid which, as can beseen, involves a number of steps.

Carrying out oxidation processes in accordance I use or relatively hightemperatures. Also there may in some instances be the disadvantage of iwith the prior art possesses a number of disad vantages exemplified, forexample, by the required polyhydroxy alcohols and other similar organiccompounds. Another and particular object of this invention is to providea direct oxidation process which may be operated at relatively lowtemperatures and under ordinary pressure conditions, yet give verysatisfactory yields of the desired oxidation products. Still anotherobject is to provides. direct oxidation process for the conversionofalcohols to acids wherein the alcohol may be converted, not only to anacid having a number of carbon atoms corresponding to the number ofcarbon atoms in the alcohol molecule,

but also to a different acid. A still further object is to Provide a,process which may be operated underother than normal atmosphericconditions, namelyfunder either superatmospherlc or reduced pressures.

A further object is to provide a direct oxidation process that may beapplied to either alcohols alone or mixtures of alcohols and aldehydes,or other types of mixtures.

' process which may be applied to various mixtures polymerization of theproducts and of 'the start-"- ing materials accompanied by lowyields'andother After further investigation I have. found thatthere arecertain other catalytic materials which may be employed in directoxidation processes in a manner akin to the procedure set forth in my ofalcohols and aldehydes wherein both the alcohol and the. aldehyde areconverted into useful goxidation products. Another object is to providea direct oxidation process, particularly adapted to the treatment ofalcohols such as butyl alcohol and the like wherein, not only maybutyric acid be obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquidsparticularly adapted for employment in the aforesaid types of processesfor U. 8. Patent No. 2,287,803 which, not only permits obtainingdirectoxidation, but permits the production of a relativelylargervariety of products than has heretofore been obtainable.

This invention has for one object to provide a process for the directoxidation of organic compounds. Another object is to provide a directoxidation process which is particularly valuable for the directconversion of lower aliphatic alcohols to lower aliphatic acids insubstantially a single step. Still another object, however, is toprovide a process which may also be applied to, not only the monohydroxyalcohols, but to the the direct conversion of alcohols alone, oralcohols in various admixtures, into useful oxidation products. A stillfurther object is to provide methods for producingithe catalysts as wellas for activating and utilizing the catalysts.

As already indicated, prior to my invention if an alcohol were to beoxidized it was generally first dehydrogenated and then the dehydrogenation products further treated. In any event prior art processes asapplied to alcohols usually invalve the utilization of temperatures inexcess of 300 C., which, not only requires substantial heat input but,due to the higher. temperatures and other conditions required inhandling chemicals,

involves dangers of loss from polymerization or other undesiredreactions. Also apparatus de struction may be more severe.

- I have found that contrary to such procedure an organic compound,exemplified in particular by a hydroxy compound as a lower aliphaticalcohol, may be directly oxidized at relatively low temperatures, eventemperatures substantially A still further object is' to provide adirect, low-temperature oxidation below 100 C., with any of the usualoxidizing mediums of which the commonest one, namely air, may be readilyutilized in my process. Also my process, after it is placed inoperation, does not usualh' require any heat input but generatessuflicient heat itself to maintain the reaction. Not only may singleorganic compounds be treated, but various mixtures of the organiccompounds may be treated. For example, I have found that a mixturecomprising a lower aliphatic alcohol, together with a corresponding or adifferent aldelnrde, may be efliciently treated by my novel process andcatalyst to give very high yields of aliphaticacid. By my process andchoice of catalyst it is possible to obtain one or more acids in theoxidation procedure. The foregoing features. as well as features oftreating various mix,- tures under different conditions, will be setforthin detail hereinafter.

While the oxidation procedure may be carried out in the apparatusdescribed in my U. S. Patent No. 2,287,803, for convenience ofconsideration and for a better understanding of the present inventionreference will be made to the attached drawing. The single figurethereof may be considered a semi-diagrammatic side elevation viewshowing a general apparatus arrangement which could be employed forcarrying out my process.

Referring to the drawing, 2 represents an oxidation unit which maycomprise any of several different constructions. For example, thepreferred external construction would, in a large diameter unit, be inaccordance with H'asche Patent 2,159,988. However, the construction maybe a sieve plate column, bubble plate column, or other comparablearrangement for permitting the contact of an oxidizing medium containingfree oxygen with the material to be oxidized. In the unit shown in theattached figure the column merely comprises an elongated open column ofrelatively narrow dimensions. Attached to the lower part of the unit at3 and l. are cooling 4 a receiver 28 at the lower part thereof and ventconduit 21 from the upper part thereof, which may lead through a meteror other device for measuring and testing the eiiluents.

There may also be associated with the apparatus thermometers or othertemperature controlling devices or various exchangers for recoveringheat or otherwise faclhtating or rendering the operation of the processmore economical, or permitting it to be operated with automatic control.in these respects.

I have found that certain metal compounds. as for example, salts derivedfrom group V metals included in the group consisting of vanadium,bismuth, tantalum, antimony, arsenic and columbium may be incorporatedin acidic solutions and that these solutions will function as a catalystmedium for the direct oxidation of organic compounds. That is, analcohol alone or an alcohol and other organic compounds to be oxidized,may be passed into a catalyst solution. as aforementioned, in thepresence of an oxidizing medium containing free oxygen and the alcoholmay be directly oxidized to acid, as will be observable from thespecific data which follow.

In preparing catalyst solutions for use in the present process, anyconvenient source of the metal may be employed, such as salts, oxides,or other derivatives thereof. Preferably, a derivative wil1 be chosenwhich is easily soluble under the conditions of the process. Forexample, assuming that it is desired to convert an aliphatic alcoholsuch as ethanol or butanol directly to the corresponding aliphatic acid,the derivative of the catalyst metal may, for example, be a compoundsuch as vanadium, bismuth, tantalum,

- antimony, arsenic and columbium jackets provided with inlets forcooling medium as at 8 and l.

The upper part of the unit was provided with a similar Jacket I;however, in this Jacket, rather .ll, l2, and I3.

As indicated, if desired in place of the external jackets, coils may beincluded within the unit and in large-size units such arrangementwherein internal coils, or both coils and jackets are employed, may bedesirable.

The lower part 'of the unit is provided with a plurality of inletconduits, namely, inlet conduit H which is connected with atemperature-controlled feed supply It. Also leading into the lower partof the unit is an inlet conduit i! for oxidizing medium.

The upper part of the unit is provided with a drawofi conduit I! whichleads through condenser l9 into separator 2!. This separator hasattached thereto a receiver 22 for condensate and a branch conduit 23through which non-condensables may be conducted to the scrubber 2|.

The aforementioned scrubber is provided with While the aforementionedmetal derivatives may be employed in various organic liquids, which aresolvents therefor, for simplicity of operation and minimizing thenecessity of complicated separations I prefer to dissolve the catalystcompound in a liquid principally composed of one of the materials whichis to be produced in the process. For'example, in the event my processwere to be applied in converting butyl alcohol directly into butyricacid I would preferably dissolve the catalyst compound in an aliphatic.acid such as butyric acid, although propionic or acetic acid could alsobe used. However, for initially preparting the catalyst solution otherliquids could be employed, as for example, organic esters and the likesuch as butyl or ethyl acetate.

In any event, irrespective of the exact metal compound and the liquidthat the compound is dissolved in, the catalyst solution would be givena vigorous oxidation treatment such as blowing with a substantial amountof air, usually for a period of at least 5 or 10 minutes, and ifdesired, for several hours. This treatment would be accompanied by'theintroduction of an aldehyde along with the oxidizing medium whichfunctions to convert the metal ions of the catalyst metal into a higherstate of valence than their lowest valence. The treatment may beaccompanied by heating obtained in any convenient manner, such as byflowing a heating medium in the jackets or coils in association with theoxidation unit or by introducing heating air. The temperature oftreatment, however, may vary from around 0 C. .up to the boiling pointof the particular liquid present. Inother words the solution ismaintained under liquid phase conditions.

It is also preferred to incorporate the oxidiz- Hence, my invention isnot to be restricted ing medium into the catalyst liquid under at leastatmospheric pressure as this permits the inclusion of a larger amount ofoxidizing medium and fully saturates the catalyst liquid.

After the catalyst liquid containing a group V metal compound as alreadydescribed has been treated and brought to a starting temperature,usually above room temperature but below about 100 0., the organiccompound to be oxidized may be supplied to the process.

That is, referring to the attached drawing, the oxidation column 2 isfilled with the catalyst liquid comprising oneor more of the group Vmetal compounds of the type described dissolved in the solvent andmaintained at the desired temperature. The hydroxy compound to beoxidized is introduced into the oxidation process through conduit l4 andthe oxidizing medium, usually air (although pure oxygen or ozone may beemployed and appear to render the catalyst solution more active, but arenot necessary), and the compound oxidized to one or more desiredoxidation products, as will be described hereinafter.

Assuming that the oxidation product is a liquid,

a portion thereof may be volatilized or pumped off through conduit itthrough the condenser 20- where condensables are condensed out to becollected in receiver 22. The unconsumed gases (as nitrogen when air isused as oxidizing medium), unoxidized organic compoxmds and the likecomponents, uncondensed, pass through conduit 23 into scrubber 14 wherethey are recovered. While only a single scrubbing .unit has beenindicated. a plurality of such units may be employed or other recoverydevices utilized.

The operation of my process to convert an or- Uanic compound such asethyl alcohol, propyl alcohol, butyl alcohol, or other aliphatic hydroxycompounds to the desired acids and the function of the group V metals asaldehyde activated catalysts is quite clearly illustrated by the dataappearing in the folowing table:

product of the oxidation, while the tion of the remaining alcohol wasleft unchanged. As indicated, while at normal atmospheric pressure, atemperature under 100 0. appears to be quite satisfactory, theparticular temperature selected will be determined largely by referenceto the particular alcohol to be oxidized and whether the process is tobe operated under pressure or merely at atmospheric pressure. Forexample, although I find a temperature range of -5 C. to 90 C.satisfactory for the oxidation of butyl alcohol to butyric acid, ifethyl or propyl alcohol is to be converted by my process, with orwithout butyl alcohol, I prefer a temperature range of C. to C.

Under preferred operating conditions as, for example, when air is usedas the oxidant, this may be supplied under some pressure and, ifdesired, a rather substantial excess may be employed, although fornormal operations merely major poran excess is required; that is, suchan amount that a few per cent of oxygen will be present in theeilluents. In the event of the use of other oxidants such as relativelypure oxygen and ozone, smaller amounts are required and may be suppliedunder substantial pressure to cause them fully to permeate the entirecatalyst solution.

The oxidation of any given alcohol in accordance with my process may beaccomplished by activating the catalyst metal in the solution by meansof a single aldehyde or by a plurality of aldehydes. For example, inoxidizing ethyl alcohol, Imay employ acetaldehyde, propionaldehyde, orbutyraldehyde alone or two or more of them. 'Moreover, I may oxidizeethyl alcohol. propyl alcohol, butyl alcohol, or amyl alcohol byemploying any one or more of aldehydes such as acetaldehyde,propionaldehyde, butyraldehyde.

and so on. However, inasmuch as acetaldehyde is in many instances mostreadily available and has a low boiling point, it would preferably beemployed along with other alcohols such as butyl alcohol, amyl alcohol,and the like, as represent- Percent G B t l Grams Grams Grams PercentPercent Metal A ta Metal Salt HAc BOBu HOP: Conversion Conversion m mCat. 001. Feed rm. rm. to HOBu to Hon- Bismuth 1 m 2,016 350.2 41.1 sso1.1 Vsuadium-.-.-..-. 1.7 420 1,260 217.3 75.2" 43-4 18.1

The foregoing examples were carried out in apparatus as indicated in theattached drawing and at a. temperature between 30 C. and 50 (3.,although a wider range of temperatures, such as -5 C. to 90"v C. couldbe employed satisfactorily. It will be observed from the above tablethat I have employed a relativel small amount of the metal acetate inthe catalyst solution in the examples given, but this may be variedrather widely. For examples, I may use anywhere from 1 or 2% of themetal acetate up to 12% or more.

While the foregoing examples are illustrative of prefered embodiments ofmy invention, it will be evident that many modifications therein may bemade within the scope of the inventive concept involved. As previouslyindicated, these catalysts may be used under the conditions outlinedabove for the conversion of various aliphatic alcohols to acids. Theymay be employed in the form of a single salt or mixtures of salts of anydesired organic acid or acids.

In the above examples, there was some small percentage of alcoholconverted to acetic acid I and some to butyl esters in addition to themain ing the most economical procedure, as well as tending to lower theboiling points and permit the functioning of the process at the lowestpractical tem tures.

As alre dy indicated, the pressure may be varied over wide limitswithout basically changing the prbcess. However, since the processfunctions satisfactorily under normal atmospheric pressures I prefer tooperate under such conditions. In some instances, such as for saturatingthe catalyst solution with oxygen, I may apply a few pounds pressure upto 2 or 3 atmospheres for this purpose. Also, as indicated, the processfunctions very well at temperatures of 5 C. to 50 or 70 C. and normalatmospheric pressure. However, by raising the temperature above therange indicated to C., for example,

the pressure should be increased in order to asbe correspondinglyreduced as the amount of alcohol fed was increased. In general, it maybe said that I prefer to carry out the process under liquid phaseconditions and at a temperature of 30 C. to 70 C.

One valuable aspect of the present invention is that acids having fewercarbon atoms than the alcohol being oxidized may be directly produced,and the proportion of these other acids to the acid having the samenumber of carbon atoms as the alcohol being oxidized may be varied bychoice of the particular catalyst.

It is apparent from the foregoing that my invention is applicable to thedirect oxidation of the various organic compounds, particularly hydroxycompounds such as various alcohols. The foregoing data are merelyillustrative of some of the materials to which my low temperature liquidphase process may be applied, but various other ccmpounds, such ashydroxy alcohols exemplified by glycols. may be treated in a comparablemanner. Hence, I do not wish to be restricted in my invention exceptinsofar as is necessitated by the prior art and the spirit of theappended claims.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. A process for the direct oxidation of a lower aliphatic alcohol toobtainthe corresponding aliphatic acid, which comprises .treating asolution of a metal ion of a group V metal selected from the groupconsisting of vanadium, bismuth, tantalum, antimony, arsenic andcolumbium in an aliphatic acid with an aldehyde and a gaseous oxidizingmedium to form an active catalyst solution, introducing material amountsof a lower aliphatic alcohol and a lower aliphatic aldehyde into theactivated catalyst solution, oxidizing the alcohol of the resultingsolution of catalyst, alcohol and aldehyde to the corresponding acid bytreating said solution with a gaseous oxidizing medium, maintaining thetemperature of the solution of catalyst, alcohol and aldehyde during itstreatment with the gaseous oxidizing medium such that the solution ismaintained in the liquid phase, and subsequently recovering thealiphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a metal ion of a group V metal selected from the groupconsisting of vanadium, bismuth, tan talum, antimony, arsenic andcolumbium in an aliphatic acid with an aldehyde and a gaseous oxidizingmedium to form an active catalyst solution, introducing material amountsof a lower aliphatic alcohol and a lower aliphatic aldehyde into theactivated catalyst solution, oxidizing the alcohol of the resultingsolution of catalyst, alcohol and aldehyde to the corresponding acid bytreating said solution with a gaseous oxidizing medium, maintainin thetemperature of the solution of catalyst, alcohol and aldehyde during itstreatment with the gaseous oxidizing medium such that the solution ismaintained in the liquid phase at a temperature of from C. to 100 C.,and subsequently recovering the aliphatic acid produced,

3. The process of claim 2 in which the catalyst, alcohol and aldehyde ismaintained during its treatment with the gaseous oxidizing medium at atemperature of 30 C. to 70 C.

4. A process for the direct oxidation of a lower aliphatic alcohol toobtain a lower aliphatic acid. which comprises treating a solution of abismuth salt in an aliphatic acid with an aldehyde and a gaseousoxidizing medium to form an active catalyst solution, introducingmaterial amounts of a lower aliphatic alcohol and a lower aliphaticaldehyde into the catalyst solution, oxidizing the alcohol of theresulting solution of catalyst, alcohol and aldehyde to thecorresponding acid by treating said solution with a gaseous oxidizingmedium, maintaining the temperature of the solution of catalyst, alcoholand aldehyde during its treatment with the gaseous oxidizing medium suchthat the solution is maintained in the liquid phase at a temperaturebelow C.. and subsequently recovering the aliphatic acid produced.

5. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a vanadium salt in an aliphatic acid with an aldehyde and agaseous oxidizing medium to form an active catalyst solution,introducing material amounts of a lower aliphatic alcohol and a loweraliphatic aldehyde into the catalyst solution, oxidizing the alcohol ofthe resulting solution of catalyst, alcohol and aldehyde to thecorresponding acid by treating said solution with a gaseous oxidizingmedium, maintaining the temperature of the solution of catalyst, alcoholand aldehyde during its treatment with the gaseous oxidizing medium suchthat the solution is maintained in the liquid phase at a temperature:below 100 C. and subsequently recovering the aliphatic acid produced.

6. A process for the direct oxidation of a lower aliphatic alcohol toobtain an acid mixture containing a major proportion of an acidcorresponding to the alcohol being oxidized and a minor proportion of anacid having a less number of carbon atoms than the alcohol, whichcomprises treating a solution of a metal ion of a group V metal selectedfrom the group consisting of vanadium, bismuth, tantalum, antimony,arsenic and columbium in an aliphatic acid with an aldehyde and agaseous oxidizing medium to form an active catalyst solution,introducing material amounts of a lower aliphatic alcohol and a loweraliphatic aldehyde into the catalyst solution, oxidizing the alcohol ofthe resulting solution of catalyst, alcohol and aldehyde to thecorresponding acid by treating said solution with a gaseous oxidizingmedium, maintaining the temperature of the solution of catalyst, alcoholand aldehyde during its treatment with the gaseous oxidizing medium suchthat the solution is maintained in the liquid phase at a temperature of-50 C. to C., and subsequently recovering the aliphatic acid produced.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,285,914 Drossbach June 9, 19422,263,607 Bludworth Nov. 25, 1941 2,287,803 Hull June 30, 1942 2,265,948Loder Dec. 9,1941

FOREIGN PATENTS Number Country Date 111,050 Australia July 25, 1940Dettifieete of Deflection Patent No. 2,425,882. August 19, 1947'.

DAVID C. L

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Column 8,line 57, for 50 C. to 150 (3.; read 5 0'. to 150 0.; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Ofiice.

Signed and sealed this 30th day of September, A. D. 19%.

it; ME

THOMAS F. i PHYQ Assistant @ommz'estooer of Patenteu

